Title: Evaluation of the effects of melting phenomenon on the residual stress formation in ferritic pipeline multi pass girth-weld joints

Authors: Djarot B. Darmadi

Addresses: School of Mechanical Engineering, University of Brawijaya, MT Haryono 167 Malang, Jawa Timur, 65145, Indonesia

Abstract: Coupled thermo-metallurgy-mechanical (TMM) analysis using FEM was carried out to represent a girth welding in ferritic pipeline steel. One of the crucial points to predict residual stress especially in multi pass welding is how to model material behaviour when melting takes place. When elements melt, they lose stiffness and also remaining plastic strain. Based on literature, it is suggested that this stiffness and plastic strain mitigation occurs even below melting temperature, known as annealing temperature. In this paper three FEM models are evaluated: 1) model without omitting stiffness and plastic strain; 2) with mitigating stiffness and plastic strain at melting point (1,400°C); 3) with mitigating stiffness and plastic strain at annealing temperature (970°C). Residual stress of two specimens was measured to validate the FEM models where model with 970°C of omitting stiffness and plastic strain showed best matching results.

Keywords: melting; annealing temperature; residual stress; ferritic steels; coupled TMM analysis; pipeline steel; pipelines; multi pass welding; girth weld joints; FEM; finite element method; material behaviour; stiffness; plastic strain.

DOI: 10.1504/IJESMS.2016.077649

International Journal of Engineering Systems Modelling and Simulation, 2016 Vol.8 No.3, pp.205 - 217

Received: 17 Dec 2014
Accepted: 23 May 2015
Published online: 12 Jul 2016 *

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